1. Field of the Invention
The invention is directed to liquid crystal side-chain polymers.
The invention is concerned with side-chain polymers having an amide group in the side-chain, their preparation, the corresponding monomers, mixtures of the polymers with one another and/or with other materials and the use of the polymers and mixtures in optics, especially in integrated optics, in optoelectronics and/or for information storage, or for the separation of mixtures of substances, especially for separating membranes for the separation of mixtures of gases or as a stationary phase in gas chromatography.
2. Description
The anisotropic properties of liquid crystals can primarily be used technically in optoelectronics. In this connection, the electro-optical indicating devices based on low-molecular liquid crystal materials have acquired particular significance. In this case, the liquid crystal serves as a light relay, whereby in general the optical behavior of the liquid crystal layer is influenced by an applied electric field. Previous investigations with respect to liquid crystals have therefore been concerned mainly with materials having a low molecular weight having regard to their applicability in indicating devices. Recently, however, investigations have also been carried out into polymers which have so-called "mesogenic" groups in the main chain of the polymer (main-chain polymers) or attached side-chain-wise to the main chain of the polymer (side-chain polymers). As the mesogen there are generally denoted groups which have a pronounced form-anisotropy and especially a rod-like or disc-like structure, since the corresponding low molecular compounds often have liquid crystalline properties [Angew. Chemie 99, 840 (1987)]. Main-chain polymers can usually form fibres of high tensile strength by parallel arrangement of the mesogenic groups. On the other hand, the lateral arrangement of the mesogenic groups in an ideal situation can lead to materials which have properties not only of polymers, but also of liquid crystals.
As materials having anisotropic properties, liquid crystal side-chain polymers are of great potential interest for the most varied technological fields. The anisotropic properties can often be modified considerably depending on the preparation and pre-treatment. For example, anisotropic glasses can be obtained by freezing the anisotropic phase or single crystals can also be obtained after previous macroscopic orientation with electric or magnetic fields. Further for example, the anisotropic properties of elastomers can also be influenced by mechanical deformation. Side-chain polymers are therefore of particular interest for optical applications, for example, as optical building elements in linear and non-linear optics, as optical storage elements and the like. On the other hand, liquid crystalline side-chain polymers are often suitable as stationary phases in gas chromatography or especially the elastomers are also suitable for the preparation of separating membranes. Further development in these fields depends essentially on the availability of specific and efficient materials.
Low molecular compounds having an amide bridging group between two rings generally have relatively high melting points. As a rule, they have no liquid crystal properties or only insufficient liquid crystal properties and have hitherto been used to a small extent. The known main-chain polymers, which have in the monomeric unit an amide bridging group between 2 rings, melt only at very high temperatures or can not be melted at all and therefore can be processed only with difficulty. Further, from Makromol. Chemie, Rapid. Commun. 6, 57-63 there is known a polysiloxane having an amide group in the side-chain, but this however, also melts only at very high temperatures with decomposition.